Organosilicon compounds having a hydrolyzable silyl group and a reactive organic group are generally referred to as silane coupling agents and often used as adhesives for bonding inorganic-to-organic materials, paint additives, and resin modifiers.
Typical reactive organic groups are vinyl, amino, epoxy, (meth)acrylic, mercapto, isocyanate, ketimine structure, and styryl groups. Silane coupling agents having such groups are well known and used in various applications.
Although silane coupling agents having a conjugated diene structure have not heretofore been reported, they constitute a class of silane materials desired in the butadiene-related industry because the conjugated diene structure is expected to have unique reactivity in contrast to the well-known functional groups.
The reason why the silane materials having a conjugated diene structure have not been reported is that hydrosilylation catalysts used in the synthesis of silane coupling agents are readily deactivated by the conjugated diene structure, failing to produce the desire compound.
Hydrosilylation reaction of adding a compound having silicon-bonded hydrogen to a compound having vinyl group in the presence of a platinum-based catalyst is a well-known technology for the synthesis or modification of organosilanes and organopolysiloxanes and for the silylation of organic compounds and organic polymers. As the means of enhancing reactivity and prohibiting rearrangement of the double bond to control the addition position, Patent Documents 1 and 2 disclose hydrosilylation reaction between a hydrogenalkoxysilane and an aliphatic unsaturated organic compound or vinyl-substituted aromatic compound in the presence of a carboxylic acid compound using a platinum catalyst. These documents relate to ordinary vinyl compounds or vinyl compounds having aromatic conjugation, but do not refer to non-aromatic conjugated dienes.
Needless to say, improvements in reactivity of hydrosilylation lead to improvements in reaction yield and improvements in productivity. When an organosilicon compound hydrosilylated on terminal carbon is used as a coupling agent or modifier, it performs better than an isomer silylated at a non-terminal position. If this organosilicon compound is an organopolysiloxane, it exhibits better physical properties such as heat resistance. Thus, there is a need for a hydrosilylation method for selectively preparing a terminally hydrosilylated organosilicon compound in high yields.